How to find settings.ini and desktop.log files:

MacOS

Settings is logcated in /Users/%username%/Library/Playkey/settings.ini while files updater and desktop are located in Users/<username>/Library(hidden folder)/playkey/desktop.log

On how to find hidden folders you can use this article

Windows

Windows XP: C:\Documents and Settings\%username%\Application Data\Playkey\

Windows 7 or newer: C:\Users\%username%\AppData\Roaming\Playkey\

First method: 

Open Windows Explorer (press Win+E), paste %APPDATA%\Playkey in the adress field and press <Enter>

Second method: 

Open "Run" command (press Win+R), paste %APPDATA%\Playkey in the field and press <Enter>